Systems and methods for treating shoulder pain related to subacromial impingement syndrome

ABSTRACT

Systems and methods are provided for treating chronic pain occurring secondarily to subacromial impingement syndrome in a human body. A system is provided to deliver percutaneous electrical stimulation through at least one electrode to neurological motor points of the posterior and middle deltoid muscles to mediate such pain. One-time, continued and/or periodic dosing of treatment methods according to the present invention may result in a change to central nervous system maladaptive neuroplasticity.

RELATED APPLICATIONS

This application claims the benefit of co-pending U.S. ProvisionalPatent Application No. 61/419,537, filed 3 Dec. 2010, and entitled“Systems and Methods for Treatment of Pain caused by SubacromialImpingement,” which is incorporated by reference herein in its entirety.

This application also claims the benefit of co-pending U.S. ProvisionalPatent Application No. 61/540,934, filed 29 Sep. 2011, and entitled“Systems and Methods for Treating Shoulder Pain Related to SubacromialImpingement Syndrome,” which is incorporated by reference herein in itsentirety.

This application is also a continuation in part of co-pending U.S.Nonprovisional patent application Ser. No. 13/095,616, filed 27 Apr.2011, and entitled “Systems and Methods for Percutaneous ElectricalStimulation,” which claims the benefit of U.S. Provisional PatentApplication 61/343,325, filed 27 Apr. 2010, and entitled “Systems andMethods for Percutaneous Electrical Stimulation,” both of which areincorporated by reference herein in their entireties.

BACKGROUND OF THE INVENTION

Shoulder pain is a common medical problem with social and economicconsequences: shoulder problems account for more than 12 million visitsto physicians annually in the US. A systematic review of literatureregarding studies on shoulder pain found that point prevalence rangesfrom about seven to about 27 percent of the general population of adultsless than 70 years of age, with one year prevalence being up to about 47percent. The wide range is attributed to inconsistent ways in which theshoulder area is defined. Annual incidence rates vary between 0.9 and2.5% of the general population depending on age. Subacromial impingementsyndrome (SIS) is the most common cause of shoulder pain, accounting for48% of incident cases. Anatomically, SIS refers to the supraspinatustendon impinging on the undersurface of the anterior acromion as the armis raised overhead. Typically, pain is generated with elevation of thearm above the head though it can occur with rest. Multiple pathologies,such as subacromial bursitis, rotator cuff tendinopathy, partial rotatorcuff tears, and even small tears can coexist to create SIS.

Shoulder pain greatly affects quality of life (QOL). One study foundthat 84% of subjects with shoulder pain slept less well, 85% hadproblems moving their arm or hand, and 45% were more irritable. Thesocioeconomic burden of shoulder pain is also substantial. Shoulderdisability can impair one's ability to work and perform household tasks,and results in, on average, 12% lost productive time from work in theUS.

Shoulder pain secondary to SIS is not adequately addressed by presenttherapies. The pain treatment continuum, especially during the acute andsubacute phases, begins with conservative treatments such asnon-steroidal anti-inflammatory drugs (NSAIDs). Though minimallyinvasive, these medications are ineffective in the long term for up tohalf of patients, and commonly have systemic side effects such asheadache, skin rash, dizziness, and gastrointestinal symptoms. Otherconservative therapies include physical therapy and injections. Whenineffective, and as the pain syndrome enters the chronic phase, theseconservative therapies are followed by opioid medications or surgicalmanagement.

Current treatment options for chronic pain also include physicaltherapies, oral analgesic medications, local injection techniques,surgery, and neurostimulation. The present treatment options demonstratemarginal pain relief and have undesired side effects. Presentneurostimulation methods have clinical and technical difficultiespreventing them from becoming the standard of care and more widelyadopted. Surface neurostimulation systems are difficult to implement dueto the discomfort of stimulation felt on the skin and the need forskilled personnel to place electrodes properly on a daily basis.Implantable neurostimulation systems (e.g., spinal cord stimulation)require placement of the device in the spinal canal (e.g. in theepidural space), which has the potential for nerve damage, unwanteddevice movement within the spinal column, and repeat clinic visits forre-adjustment. Historically, peripheral nerve stimulators for pain havenot achieved widespread clinical success, due to the need to dissect orexpose nerves in an open surgical procedure and place leads directly incontact with these target nerves.

Thus, currently available therapies are unsatisfactory in treatingshoulder pain. Forty to fifty percent (40-50%) of patients who visit ageneral practitioner continue to report shoulder pain after 12 months ofconservative therapy. Currently there is no commonly accepted standardof care for shoulder pain. Rest (avoiding offending movements such aselevation of the arm over the head), non-steroidal anti-inflammatorydrugs, physical therapy, and corticosteroid injections are most commonlyused for treating shoulder pain secondary to SIS, regardless of theexact pathology. When these fail, surgery is considered, but surgicalpain management due to SIS is no more effective than conservativetherapies, leaving 40-50% of patients without an effective treatment fortheir chronic pain.

Accordingly, the art of shoulder pain therapy would benefit from safeand effective short- and long-term peripheral nerve stimulation (PNS)therapies for patients with moderate to severe acute, sub-acute and evenchronic (>6 month) shoulder pain secondary or related to SIS.

SUMMARY OF THE INVENTION

Embodiments according to the present invention are adapted to providesafe and effective short- and long-term peripheral nerve stimulation(PNS) therapies for patients with moderate to severe acute, sub-acuteand even chronic (>6 month) shoulder pain secondary or related to SIS.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an anatomical view of a human shoulder joint.

FIG. 2 is a perspective assembly view of an embodiment of an electricalstimulation system according to the present invention.

FIG. 3 is a perspective assembly view of an embodiment of a mountingpatch according to the present invention.

FIG. 4A is a perspective assembly view of an embodiment of a patchbattery assembly according to the present invention.

FIG. 4B is a perspective view of an assembled embodiment of a patchbattery assembly according to the present invention.

FIG. 5A is a perspective view of an embodiment of an electricalstimulator according to the present invention.

FIG. 5B is a front elevation view of the embodiment of FIG. 5A.

FIG. 5C is a rear elevation view of the embodiment of FIG. 5A.

FIG. 5D is a bottom plan view of the embodiment of FIG. 5A.

FIG. 5E is a top plan view of the embodiment of FIG. 5A.

FIG. 6 is an assembly view of the embodiment of FIG. 5A.

FIG. 7 is a block level schematic representation of electricalstimulation generation circuitry provided in the embodiment of FIG. 5A,further coupled to a schematic representation of the patch batteryassembly of FIG. 4C.

FIG. 8 is an embodiment of a waveform to be generated by stimulationpulse generation circuitry according to the present invention.

FIG. 9 is a perspective view of the electrical stimulator of FIG. 5Aphysically and electrically coupled to the patch assembly of FIG. 3.

FIG. 10 is an elevation view of a first embodiment of a cable accordingto the present invention.

FIG. 11 is an elevation view of a second embodiment of a cable accordingto the present invention.

FIG. 12 is an elevation view of a third embodiment of a cable accordingto the present invention.

FIG. 13A is a perspective view of a first embodiment of an insulationdisplacement connector according to the present invention.

FIG. 13B is a partial assembly view of the connector of FIG. 13A.

FIG. 14 is a second partial assembly view of the connector of FIG. 13A.

FIG. 15 is a first perspective view of the assembly of FIG. 14 furtherassembled.

FIG. 16 is a cross-section view taken along line 16-16 of FIG. 13A,further showing conductors installed.

FIG. 17 is a perspective view of an embodiment of a connector mountingstructure according to the present invention.

FIG. 18 is an elevation view of an embodiment of a percutaneous leadaccording to the present invention.

FIG. 19 is a perspective view of an introducer according to the presentinvention.

FIG. 20 is a perspective view of the introducer of FIG. 19 loaded withthe lead of FIG. 18.

FIG. 20A is a partial perspective view of an embodiment of an introducerneedle according to the present invention.

FIGS. 21 and 22 are anatomical views of a patient's shoulder showing theplacement of a needle electrode placed in proximity to motor point A anda needle electrode placed in proximity to motor point B.

FIG. 23 is an anatomical view of the shoulder as shown in FIG. 22,showing a pulse generator coupled to one needle electrode and to thereturn electrode so that test stimulation may be delivered to stimulatethe desired motor point.

FIG. 24 is an anatomical view of the shoulder as shown in FIG. 22,showing the location at which both muscle A and muscle B can beactivated simultaneously using one electrode, by placing a needleelectrode at the approximate midpoint between the prior identifiedlocations of needle electrodes for muscle A and muscle B respectively.

FIG. 25 is an anatomical view of the shoulder as shown in FIG. 22,showing the intramuscular lead and electrode placed percutaneously inthe shoulder via an introducer needle.

FIG. 26 is an elevation view of a system according to the presentinvention mounted on a user patient's arm.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Although the disclosure hereof is detailed and exact to enable thoseskilled in the art to practice the invention, the physical embodimentsherein disclosed merely exemplify the invention which may be embodied inother specific structures. While the preferred embodiment has beendescribed, the details may be changed without departing from theinvention, which is defined by the claims.

Turning now to the figures, FIG. 2 depicts components of one or moreelectrical stimulation systems according to the present invention.Preferably, an electrical stimulation system 10 according to the presentinvention includes a mounting patch assembly 100, an electricalstimulator 200, one or more electrical cables 300, and one or morestimulating electrodes 402 that may be carried on a percutaneouselectrical lead 400. Embodiments according to the present invention alsoinclude electrical connectors 500 and connector mounting structure 600.

As used herein, the term “percutaneous” is to be understood to describean electrical stimulation that is provided to animal tissue, where thesource of the stimulation (e.g. device/tissue interface) is an electrodethat is positioned subepidermally. Percutaneous stimulation may beprovided a number of ways, such as by an electrical conductor (e.g.,wire) configured to be utilized while protruding through the epidermisof the animal. Alternatively, percutaneous stimulation may be providedby an implanted electrode that is wirelessly controlled and/or poweredby a control unit positioned outside of the animal body.

The term “percutaneous” may be contrasted with the term“transcutaneous,” which is conventionally understood to involve theapplication of electrical stimulation to an animal body throughelectrodes (e.g. surface electrodes or EKG electrodes), which are inelectrical contact with the epidermis of the animal. While generallypreferred embodiments according to the present invention include systemsand methods of percutaneous stimulation, it is to be understood thatvarious components of systems according to the present invention may beutilized in other methods of stimulation, such as transcutaneousstimulation, and even outside the field of electrical stimulationaltogether.

While a percutaneous system is herein described, it is to be understoodthat applicable treatments may be provided initially by suchpercutaneous system and, if desirable, treatments may be continuedthrough the use of an implantable electrical stimulator, where suchstimulator and stimulation is contained entirely under the epidermis ofthe animal.

Patch Assembly

FIG. 2 provides an assembly view of a preferred patch assembly 100according to the present invention. The preferred patch assembly 100 iscomprised of several layers, including an adhesive layer 102, anelectrode layer 104, a reinforcement layer 106, and a cover layer 108.All of the layers 102,104,106,108 are preferably substantially the samelength and width, so as to form a generally uniform stack of layers whenassembled. The adhesive layer 102 is preferably formed from a desiredthickness (e.g. such as about 20 to about 30 mils, with about 25 milsbeing most preferred) of electrically conductive hydrogel. The electrodelayer 104 is a conductive material, preferably formed from a carbon orcarbon/silver film of a desired thickness, such as about 2.35 mils. Thereinforcement layer 106 is preferably formed from a polyethylene filmcoated on one side 106 a with a contact pressure sensitive acrylicadhesive. The reinforcement layer 106 and adhesive is preferablyprovided at a desired thickness, such as about five to about six mils.The cover layer 108 is preferably a durable tape material, whichpreferably has a matte, or non-reflective finish. An example ofdesirable tape material is a polyester fabric tape of a desiredthickness, such as about 13 mils. The overall length 101 and width 103of a preferred patch assembly 100 according to the present invention areabout 2.5 inches by about 2.5 inches, respectively, and more preferablyabout 2.625 inches by about 2.5 inches respectively. Provided as aprotective cover to the adhesive layer 102 may be an adhesive neutralliner 105, such as a silicone coated polyester film of a desiredthickness, such as about four mils.

Also preferably provided on the patch assembly 100 is a power source,such as a battery assembly 110. The battery assembly 110 may bepositioned and held securely substantially between two of the layersalready described, such as between the conductive layer 104 and thereinforcement layer 106. The battery assembly 110 is preferably formedfrom one or more conductor assemblies 112,114 and a battery 116. Thebattery 116 has a preferred capacity and provides a desired voltage,such as about fourteen milliamp-hours and about two to about threevolts, respectively, and is provided with a first terminal 118 and asecond terminal 120. However, a stimulator 200 according to the presentinvention may function with a battery providing as little as 6.8 mA-hrdown to a voltage of about 2.4 volts. A preferred battery is a flexiblelithium polymer primary cell battery, such as an SF-2529-14BC batteryavailable from Solicore, Inc., of Lakeland, Fla. A preferred battery 116preferably has a size of about 25 millimeters by about 30 millimeters byabout 0.5 millimeters, with a size of 26 mm×29 mm×0.45 mm being mostpreferred.

A first conductor assembly 112 is formed from a snap member 122 coupledto a copper foil conductor 124. The copper foil conductor 124 ispreferably substantially L-shaped having a substantially rectilinearbody portion 124 a formed along a longitudinal axis 125 and a legportion 126 extending preferably co-planar from the body portion 124,preferably orthogonal to the longitudinal axis 125. The body portion 124may be folded onto itself to form a dual layer portion 124 b withenhanced durability and support for the snap member 122. A preferredsnap member 122 is preferably a male conductive snap assembly includinga shank member 122 a and a receiver member 122 b. The shank member 122 ais at least partially received into the receiver member 122 b andsecured thereto. Preferred receiver members 122 b are formed from nickelplated brass configured to mate with conventional 4 mm medical industrystandard parallel spring female snaps. Preferred shank members 122 a aresilver or silver chloride coated molded plastic substrate. The shankmember 122 a is positioned through a snap aperture 130 formed throughthe copper foil conductor assembly 124, such as through the dual layerportion 124 b. The snap aperture 130 may be formed prior to insertion ofthe shank member 122 a, or may be formed by or simultaneously with theinsertion of the shank member 122 a through the foil conductor 124.

A second conductor assembly 114 is also formed from a snap member 132coupled to a copper foil conductor 134. The copper foil conductor 134 ispreferably substantially U-shaped with a first leg 136 coupled to asecond leg 138 through a base portion 140. The first leg 136 is formedin a preferably substantially rectilinear formation having a length 136a disposed along a first leg axis 137, and a width 136 b measuredperpendicular to the first leg axis 137. The second leg 138 is formed ina preferably substantially rectilinear formation having a length 138 adisposed along a second leg axis 139, and a width 138 b measuredperpendicular to the second leg axis 139. The second leg axis 139 ispreferably disposed at least substantially parallel to the first legaxis 137. The first leg length 136 a is preferably substantially similaror equal to or less than the second leg length 138 a. The first leg 136may be folded onto itself to form a dual layer portion 136 c withenhanced durability and support for the snap member 132. The first leg136 and the second leg 138 are preferably disposed at leastsubstantially coplanar with each other and electrically coupled by thebase portion 140, spacing the first leg 136 from the second leg 138 by apreferred insulative gap 142. Extending from the second leg 138 into theinsulative gap 142, preferably perpendicular to the second leg axis 139,is a conductor tab 144, configured to be folded over the battery 116 andsoldered to the second battery terminal 120. A preferred snap member 132is preferably a male conductive snap assembly including a shank member132 a and a receiver member 132 b. The shank member 132 a is at leastpartially received into the receiver member 132 b and secured thereto.Preferred receiver members 132 b are formed from nickel plated brassconfigured to mate with conventional 4 mm medical industry standardparallel spring female snaps. Preferred shank members 132 a are silveror silver chloride coated molded plastic substrate. The shank member 132a is positioned through a snap aperture 146 formed through the first leg136, such as through the dual layer portion 136 c. The snap aperture 146may be formed prior to insertion of the shank member 132 a, or may beformed by or simultaneously with the insertion of the shank member 132 athrough the foil conductor 134.

To assemble the battery assembly 110, the first conductor assembly 112may be punched or otherwise cut or formed from a copper material and thesnap member 122 coupled thereto. The first conductor assembly 112 isadhered to the battery 116, and the leg portion 126 is electricallycoupled, such as by soldering, to the first battery terminal 118,thereby placing the snap 122 in electrical contact with the firstterminal 118. The battery 116 is adhered to the second conductorassembly 114, preferably to the second leg 138, and the conductor tab144 is electrically coupled, such as by soldering, to the second batteryterminal 120, thereby placing the snap 132 in electrical contact withthe second terminal 120. The second copper foil conductor 134 is placedin electrical communication with the conductive layer 104, such as byfrictional contact or conductive adhesive, and the battery assembly 110is preferably adhered to the conductive layer 104 and covered by thereinforcement layer 106 and the cover layer 108. Snap apertures 145 arecut, drilled, or otherwise formed through the reinforcement layer 106and the cover layer 108 to align with the locations of the snap members122,132 on the battery assembly 110.

FIG. 3B is a perspective view of an assembled battery assembly 110. Onceassembled, the battery assembly 110 preferably offers the pair of snaps122,132 spaced at a snap spacing 147 and provided substantially coplanarand lying in a line 149 that is at least substantially directionallyperpendicular to the second leg axis 139. The source resistance of thebattery 116 and its construction are such that overheating of thebattery 116 is preferably not possible even with shorted terminals118,120.

Electrical Stimulator

Turning now to FIGS. 4A-5, an embodiment 200 of an electrical stimulatoraccording to the present invention may be described. Generally, thestimulator 200 includes a housing 201 having a cover 202 and a base 204.The housing 201 generally forms a cavity 203 that is configured to atleast partially contain a printed circuit board 206 on which electricalstimulation generation circuitry may be mounted. Generally, the housing201 extends between and includes a front surface 208 and an opposed backsurface 210, a top surface 212 and an opposed bottom surface 214, and aleft surface 216 and an opposed right surface 218. The housing 201 mayhave a plurality of apertures or passageways 205 formed therethrough,allowing access to the cavity 203, either functionally or physically.Functional access may be provided to a user output interface, such as adisplay screen 220, or to a user input interface, such as one or morebuttons or keys 222 a,222 b,222 c,222 d. Physical and/or functionalaccess may be provided such as for one or more slide switches 224 orelectrical connection, such as by way of a jack 226. The housing 210preferably includes a housing thickness that may be measured between andinclude the front surface 208 and the back surface 210. The housing 201may have a first thickness 227 and a second thickness 228, which isgreater than the first thickness 227. If buttons 222 extend through thefront surface 208 or the rear surface 210, the second thickness 228 ispreferably greater than the sum of the first thickness 227 and anybutton thickness 229, measured perpendicular to the front surface 208 orrear surface 210, respectively. Such greater second thickness 228assists in protecting from accidental engagement of the buttons 222 bybumping the stimulator 200 against something or from clothinginteraction if the stimulator 200 is worn under a person's clothes.

Mounting structure 230 is preferably provided on or coupled to the backsurface 210 of the housing 201. The mounting structure 230 preferablycorresponds to mounting structure provided on the patch assembly 100, asdescribed above, such as the snap members 122,132. Accordingly, themounting structure 230 is preferably comprised of two female parallelspring snap members 232 spaced at a mating snap spacing 233, which issubstantially the same as or equal to the snap spacing 147 provided onthe patch assembly 100. As depicted, the mating snap spacing 233 may beprovided off-center, that is, positioned closer to one of the left side216 or right side 218 of the housing 201. Such arrangement may bepreferable to enable centering of the stimulator 200 on the patchassembly 100, which is a preferred mounting arrangement. As mentionedabove, a power source may be provided in a patch assembly 100, such asthe battery 116. Electrical connection between the patch assembly 100and the electrical stimulator circuit board 206 may be provided throughthe snap members 122,132,232. Within the housing 201, the female snapmembers 232 may be electrically coupled to the printed circuit board206, e.g. through a plurality of wires 234. Alternatively, thestimulator 200 may be mounted to the patch assembly 100 through the snapmembers 122,132,232 for structural support or mounting only, and a powersource, such as a lithium ion cell, could be provided within the housing201. In such case, it would be unnecessary to electrically couple thefemale snap members 232 to the printed circuit board 206.

As mentioned, the housing 201 may provide functional access to a useroutput interface such as a liquid crystal display 220. The LCD 220 maybe backlit or not backlit. Provided over the LCD may be a substantiallyplanar, preferably transparent, cover or lens 236. A user inputinterface may also be provided by the one or more buttons 222 and/orslide switch 224. The one or more buttons 222 each correspond to apushbutton switch 238, which may be mounted on the printed circuit board206 and electrically coupled to a microcontroller. The slide switch 224may also be mounted to the printed circuit board 206 and electricallycoupled to the microcontroller. Usage of the user input interface willbe more fully described below. The housing cover 202 is preferably heldin mechanical engagement with the housing base 204 by a plurality ofthreaded fasteners 240.

Turning to FIG. 6, various circuit elements of a preferred stimulator200 may be understood. As described, a preferred stimulator 200 includestwo female parallel spring snaps 232 that mate with the two male snaps122,132 on a preferred patch assembly 100 in either orientation,regardless of polarity. A battery power rectifier 250 provides a lowloss circuit that takes either polarity of connection to the patchassembly 100 and completes an electrical connection between theconductive layer 104 and a ground connection of the stimulator circuitryand a positive battery terminal to the VBAT connection of the stimulatorcircuitry. This circuit element requires no external control or powerand only needs connections to the battery and load.

A VCC power supply 252 provides power to a microcontroller 254. Themicrocontroller 254, and indirectly the LCD 220, the pushbutton andswitch sensing circuitry, and a controlled current sink 256 of theoutput stage, all receive their power from the VCC power supply 252. Themicrocontroller 254 and the other circuit elements are designed tofunction correctly and within specifications over the entire range ofacceptable battery voltages. The flash memory of the microcontroller254, on the other hand, may be more sensitive to voltage variation, suchas disallowing programming or erasure if VCC falls below 2.70 volts.Accordingly, the VCC power supply 252 includes circuitry to boost thebattery voltage to about 3.3V, upon request by the microcontroller 254,when VCC directly generated from the battery voltage drops below 2.80V.The 0.10V difference between VCC=2.80V (where the VCC power supplybegins boosting the battery voltage) e and VCC=2.70V (below which themicrocontroller 254 cannot reliably program its flash memory) ensurescorrect operation even with the tolerance with which the microcontroller254 can measure VCC. Specifically, the VCC power supply 252 has twomodes of operation: Battery Voltage Pass-through operation and ChargePump operation.

The microcontroller 254 places the VCC power supply 252 in the batteryvoltage pass-through mode at all times except when the sensed batteryvoltage is less than 2.80V and a flash memory erase or write operationmay be required. In this pass-through mode, the battery voltage isconnected directly to VCC through turned ON MOSFET switches. This allowsan efficient generation of VCC with very little power loss.

The microcontroller 254 places the VCC power supply 252 in the chargepump mode only when sensed battery voltage is less than 2.80V and amicrocontroller flash memory write or erase operation is likelyrequired. In this charge pump mode, the VCC power supply 252 has asignificant current drain in addition to the VCC current. Accordingly,this mode is preferably only used when required and represents a verysmall percentage of the total operating time of the stimulator 200.

An example of a microcontroller 254 that may be used in the stimulator200 is a Texas Instruments MSP430FG437. The microcontroller 254 usespreferably embedded firmware that controls the operation of thestimulator 200. The firmware is preferably saved in non-volatile (flash)memory which preferably cannot be modified by the end user of thedevice. In addition to the operating program stored in the flash memory,stimulus parameters programmed for and end user patient and the historyof usage and errors are also preferably stored in other sections of theflash memory. The microcontroller 254 is responsible for the control ofessentially all of the controllable electronic hardware of thestimulator 200: the sequence and timing of stimulus generation,interactions with user via slide switch, pushbutton, and the LCD screen,and for monitoring operation of the hardware to identify failures orunsafe operation.

The microcontroller 254 includes connections to a 32.768 KHz quartzcrystal 258, which provides a precise clock source. This precision clocksource is used to time the slower stimulus features (interval betweenpulses, duration of burst and gap, etc.). It is also used as part of afrequency-locked-loop to ensure that the high speed clock of themicrocontroller 254 is correctly calibrated. This high speed clock isused to time the stimulus pulse duration, the interphase delay, and therelatively short times required for hardware activation, deactivation,settling, etc. Preferred pulse durations may be on the order of about 20microseconds to about 200 microseconds. Most of these timing functionsmake use of timer hardware inside the microcontroller 254 that enablesprecise timing, including the generation of hardware I/O logic changeswithout software intervention after the timer is configured.

A 12-bit ADC (analog to digital converter) is provided in themicrocontroller 254 and is used to measure VCC (and thus the batteryvoltage), the value of VCC when the charge pump is enabled, the value ofthe heavily filtered battery voltage driving a VHH power supply 260, andthe value of VHH before, during, and after each stimulus pulse. Theseconversions are made using an external voltage reference 262 as eitherthe reference for the conversion or the input using VCC as the referencefor the conversion. This allows the precise measurement of these analogsignals even with varying battery voltages.

Two 12-bit DAC (digital to analog) outputs are also provided by themicrocontroller 254 and are used to program the requested voltage forthe VHH Power supply 260 and to program a requested cathodic phasecurrent generated by the controlled current sink 256.

The microcontroller 254 preferably automatically drives the segments andtwo backplanes of the LCD 220 taking segment values (on or off) andgenerating the necessary segment and backplane voltages for a preferably½ duty cycle multiplexed LCD. The microcontroller 254 can also makesmall changes to LCD biasing voltages to correct for changes in batteryvoltage or ambient temperature if necessary.

The lockout slide switch 224 and the one or more, preferably four,momentary contact pushbuttons 238 are logic inputs to themicrocontroller 254 (preferably provided with software de-bouncing theswitches).

The VHH power supply 260 is enabled by the microcontroller 254 (vialogic control lines) and charges to a voltage set by the microcontroller254 (via a DAC output signal). The VHH power supply 260 is a low powerboost DC-DC converter with a single inductor. The VHH power supply 260is unique in that under microcontroller control (and timing) the VHHpower supply 260 can be activated (generating the requested voltage),deactivated (not actively generating VHH, but holding VHH up with anominal 1.8 μF of output capacitance), or floating (in which case theVHH is not actively being generated and is held up by only about 1 nF ofoutput capacitance). This unique design can be used to generate thestimulus current waveform as described below. The VHH power supply 260may use a Linear Technology LT1615-1 as the SMPS (Switch Mode PowerSupply) chip with a Schottky diode for rectification.

The SMPS chip has a relatively large (330 μF) bypass capacitor on itsinput voltage pin that provides the energy necessary for generating VHH.The source resistance of some lithium batteries provides a basis forusing the large bypass capacitor, averaging the 100 mA peak currentrequired by the SMPS to 1 mA to 2 mA from the battery. A MOSFET switchisolates the large bypass capacitor from the battery, and twomicrocontroller IO pins with series resistors charge the large capacitorslowly to the battery voltage before the discrete MOSFET is enabled.

A low power precision voltage reference 262 (which may be a TexasInstruments REF3012) is provided with power by I/O pins of themicrocontroller 254 acting as power output lines. This is possiblebecause of the low operating current of this voltage reference. Thereference voltage is used to make analog voltage measurements with the12-bit ADC of the microcontroller 254 and to set the voltage of VHH andthe stimulus amplitude (cathodic phase current) through the two DACoutputs. A preferred stimulus amplitude ranges from about 0.1 milliampto about 20 milliamps, preferably configurable in increments of 0.1milliamps to 1 milliamp.

A controlled current sink circuit 256 is a closed loop circuit using anN-channel MOSFET inside a feedback loop of an operational amplifier withlogic shutdown control. The microcontroller 254 first provides power tothe circuit (i.e., to the op amp) and sets the desired current level viaa DAC signal. The microcontroller 254 then generates precisely timedpulse to enable the operational amplifier and to sink the specifiedamplitude from VHH to circuit common, or circuit ground.

FIG. 7 depicts a waveform of a preferred electrical stimulus current,which is preferably a biphasic, controlled current cathodic phase withan interphase delay interval of 100 μsec and a capacitor coupledrecovery phase. The stimulus current, which is provided preferably at afrequency of about 5 Hz to about 25 Hz, is generated by the followingoperating conditions and sequence of events:

During stimulation and in the gaps between stimulus pulses, VHH is heldup by the switched 1.8 μF output filter capacitor of the VHH powersupply 260.

The VHH SMPS is periodically enabled to keep VHH near its desired value.VHH slowly discharges through the resistive voltage dividers of the SMPSand the VHH voltage sampling circuit.

The output coupling capacitor, a nominal 1.8 μF, is normally charged toVHH.

Preferably immediately before a stimulus pulse, the 1.8 μF output filtercapacitor of the VHH power supply is isolated (disconnected from thecircuit).

When the controlled current sink 256 is enabled for the stimulus pulseduration, the current comes from the output coupling capacitor passingcurrent through the patient electrode circuit. This discharges thecapacitor by Q/C (a little more than 2V for the maximum charge stimuluspulse).

During the interphase delay interval, the controlled current sink hasbeen disabled and there is not significant current flow through thepatient circuit.

At the beginning of the recovery phase, the output filter capacitor ofthe VHH power supply is again enabled (returned to the circuit) and thenthe VHH SMPS is enabled, pulling VHH back to its original value andreturning the charge from the patient circuit.

Hardware-Software Partitioning & Software Detection of Hardware Failures

Refreshing and multiplexing of the segments and backplanes of the LCD220 is preferably accomplished by the microcontroller 254 and a resistordivider network. The generation of the cathodic phase current (i.e.,enabling the controlled current sink 256) is preferably started andstopped by timer hardware within the microcontroller 254. Sampling ofthe VHH during the cathodic phase is also preferably invoked by timerhardware of the microcontroller 254. The hardware is preferablyconfigurable and configured by software, as is the overall timing andsequencing of hardware to make stimulus pulses with desired timings forramp, burst, ramp, and gap sequence portions.

The operating software is also preferably responsible for periodicmonitoring of hardware status to ensure that the stimulator 200 isoperating correctly and without hardware failures that have safetyimplications. Various specific monitoring may be desirable, e.g.:

At power ON, the integrity of the flash memory may be tested andverified. If the flash memory may have been corrupted, the stimulator200 may prevent enablement of VHH generation and will remain OFF.

At power ON, the integrity of microcontroller RAM memory may be testedand verified. If the RAM memory is not functional, the stimulator 200may prevent enablement of VHH generation and will remain OFF.

VCC (Battery Voltage) may be measured before every stimulus pulse andstimulation may be suspended if the battery voltage is inadequate toensure the pulse will be safely generated by the charge already in the330 μF input filter capacitor of the VHH power supply 260.

VCC may be measured before each write or erase of flash memory that mayrequire the operation of the charge pumped VCC. Stimulation may besuspended if the value is outside specified limits.

The value of VHH may be measured before, during and/or after eachstimulus pulse. These voltages may be tested to confirm that the VHHvoltage measured is within specifications of the voltage requested. Ifthe voltage is outside of a desired range of acceptable values,stimulation may be suspended and VHH may be shutdown. These voltages mayalso be tested to detect an open electrode circuit, which alsopreferably suspends stimulation and shuts down VHH. Lastly, the sag inVHH between stimulus pulses (or between refresh cycles that bring VHHback up to the desired value) may be measured to verify that current isnot flowing (potentially through the patient) when it should not be.

FIG. 8 depicts a stimulator 200 according to the present inventionmechanically mounted to a patch assembly 100 according to the presentinvention.

Cables

FIGS. 9-11 depict various cable embodiments 300 according to the presentinvention. A first cable embodiment 300, shown in FIG. 9, generallyincludes a single conductive path extending between and including afirst connector element 302 and a second conductor element 304. Thefirst connector element 302 is preferably a touchproof pin connectorhaving a conductive pin of a first diameter, such as about 1.0millimeter. The second connector element 304 is preferably also atouchproof pin connector having a conductive pin of a second diameter,which is preferably different from the first diameter, such as beinggreater than the first diameter. The second diameter is preferably about1.5 millimeters. The provision of different connector pin diameters ispreferred to aid in preventing reversal of the cable 300 during use.Additionally, the first connector element 302 may be provided as a firstcolor, such as a color that corresponds to a color of the stimulatorhousing 201, such as white, and the second connector element 304 may beprovided as a second color, which is different from the first, thesecond color being, e.g., black. The pins in the connector elements302,304 are preferably electrically connected by an insulated electricalwire 306 disposed therebetween. A preferred insulated wire 306 may be asingle tinsel wire (nominal resistance of about 0.20 ohms/foot) having apreferred overall diameter of about 50 mils and a preferred nominaltensile break strength of about 33 pounds. The cable 300 may be providedalong a preferred length end-to-end, such as about thirteen to aboutfifteen inches. Multiple embodiments of the first cable 300 may beprovided in a kit so as to provide different lengths of the cable 300,such as about six inches. The first connector element 302 is preferablymateable with the jack 226 provided on the stimulator 200. The secondconnector element 304 may be mateable with an intermediate cable (suchas intermediate cable 300″ described below) or directly with apercutaneous lead 400.

A second cable embodiment 300′, shown in FIG. 10, generally includes asingle conductive path extending between and including a first connectorelement 302′, a second conductor element 303′, and a third connectorelement 304′. The first connector element 302′ is preferably atouchproof pin connector having a conductive pin of a first diameter,such as about 1.0 millimeter. The second connector element 303′ ispreferably an alligator clip, which may be provided in a desirablecolor, such as red. The third connector element 304′ is preferably alsoa touchproof pin connector having a conductive pin of a second diameter,which is preferably different from the first diameter, such as beinggreater than the first diameter. The second diameter is preferably about1.5 millimeters. The provision of different connector pin diameters ispreferred to aid in preventing reversal of the cable 300′ during use.Additionally, the first connector element 302′ may be provided as afirst color, such as a color that corresponds to a color of thestimulator housing 201, such as white, and the third connector element304′ may be provided as a second color, which is different from thefirst, the second color being, e.g., black. The pins in the connectorelements 302′,304′, and the second connector element 303′, arepreferably electrically connected by insulated electrical wire 306′disposed therebetween and spliced by a bifurcation connector 308′. Apreferred insulated wire 306′ may be, e.g. a 24 gauge stranded copperwire (nominal resistance of about 0.03 ohms/foot) having a preferredoverall diameter of about 50 mils and a preferred nominal tensile breakstrength of about eleven pounds. The wire 306′ may be provided along apreferred length between the first connector element 302′ and thebifurcation connector 308′, such as about fifteen to about sixteeninches. The first connector element 302′ is preferably mateable with thejack 226 provided on the stimulator 200. The third connector element304′ may be mateable with an intermediate cable (such as intermediatecable 300″ described below) or directly with a percutaneous lead 400.

FIG. 11 provides an intermediate cable 300″ according to the presentinvention. The intermediate cable 300″ generally includes a singleconductive path extending between and including a first connectorelement 302″, and a second connector element 304″. The first connectorelement 302′ is preferably a touchproof pin receiver connector (ortouchproof female connector) having a conductive sleeve adapted toreceive a pin of a first diameter, such as about 1.5 millimeters. Thesecond connector element 304″ is preferably a crimpable terminationconnector, such as a piece of stainless steel tubing material having anexternal diameter of about 50 mils and an internal diameter of about 42mils, or 18 gauge. The connector elements 302″,304″ are preferablyelectrically connected by insulated electrical wire 306″ disposedtherebetween. A preferred insulated wire 306″ may be, e.g. tinsel wire,having a preferred overall diameter of about 50 mils. The wire 306″ maybe provided along a preferred length end-to-end, such as about seven toabout nine inches. The first connector element 302″ is preferablymateable with a touchproof pin connector, such as connector element 304or 304′, previously described. The second connector element 304″, afterbeing crimped onto a stripped portion of the wire 306″, is preferablymateable with an insulation displacement connector 500 as hereinafterdescribed, or directly with a percutaneous lead 400.

Cable Connector

With reference to FIGS. 12A-15, a preferred insulation displacementconnector 500 may be described. Such connector may be found in U.S.patent application Ser. No. 12/958,077, filed on Dec. 1, 2010, which isincorporated by reference herein in its entirety. The connector 500generally includes a connector body 510 and a coupling element 550. Theconnector body 510 may be formed of any desirable shape, but ispreferably formed substantially as a parallelepiped having a frontsurface 512 oppositely disposed from a rear surface 514, a left surface516 oppositely disposed from a right surface 518, and a top surface 520oppositely disposed from a bottom surface 522. The front surface 512 maybe situated at a body width 524 from the rear surface 514, the leftsurface 516 may be situated at a body length 526 from the right surface518, and the top surface 520 may be situated at a body thickness 527from the bottom surface 522. The body width 524 is preferably about 0.25inches to about 0.75 inches, more preferably about 0.30 inches to about0.50 inches, and most preferably about 0.40 inches. The body length 526is preferably about 0.50 inches to about 1.00 inches, more preferablyabout 0.50 inches to about 0.75 inches, and most preferably about 0.625inches. The body thickness 527 is preferably about 0.15 inches to about0.50 inches, more preferably about 0.20 inches to about 0.30 inches, andmost preferably about 0.25 inches.

While the connector body 510 may be formed of any desirable materialthat may be selected for a given use, the connector body 510 ispreferably formed from an electrically insulative material, such as athermoplastic material, which may be a USP Class VI medical gradeplastic material. A preferred material may be selected from the Ultem®family of amorphous thermoplastic polyetherimide (PEI) available fromSabic Innovative Plastics Holding BV, of Pittsville, Mass., and also ofthe Netherlands. A preferred material is Ultem 1000. Indeed, theconnector body 510 may be machined from Ultem bar stock having a desireddiameter, such as about 0.625 inches, which may cause the left surface516 and right surface 518 to be generally convex along the body width524.

Formed into the connector body 510 is at least one engagement aperture,bore or channel 528, formed along an engagement axis 530. The engagementaperture 528 is provided with an engagement means 532, such as threads534, to cooperate with the coupling element 550. The engagement aperture528 may be formed through the connector body 510, such as through theentire width 524, as shown. The threads 534 may be formed during castingof the body 510 or in a machining process after the body 510 has beencast or machined.

Also formed into the connector body 510 is at least one conductoraperture, bore or channel 536. In the embodiment shown, a firstconductor channel 538 is formed into the front surface 512 of theconnector body 510, the first conductor channel 538 being formed along afirst conductor axis 539 which may be disposed at least substantiallyparallel to the engagement axis 530. The first conductor channel 538 ispreferably a smooth reentrant bore, which is formed at a distance fromor relation to the engagement aperture 528 so as to intersect theengagement aperture 528. As shown, the first conductor axis 539 isdisposed substantially parallel to the engagement axis 530, and spacedtherefrom by a distance that is preferably less than the sum of theradius of each of the axes 530,539 such that the first conductor channel538 overlaps the engagement aperture 528 longitudinally along a lengththereof. A portion 538 a of the first conductor channel 538 preferablyextends through the connector body 510, and such arrangement may bedesirable to provide for conductor length adjustment. The portion 538 amay extend substantially directionally perpendicularly to a tangent ofthreads 558 provided on the stud 552, as further described below.

In the first embodiment 500, a second conductor aperture, bore orchannel 540 is formed along a second conductor axis 542. While thesecond conductor bore 540 may extend through the entire connector body510, such as through the entire body length 526, the second conductorbore 540 is preferably a smooth reentrant bore, which at least partiallyintersects the engagement aperture 528. The second conductor axis 542may be coplanar with the engagement axis 530, but is preferablyperpendicularly skew to the engagement axis 530 at a desired angle.Thus, in the embodiment 500 shown, using the engagement axis 530 as areference, the first conductor axis 539 is disposed substantiallyparallel to and below the engagement axis 530, while the secondconductor axis 542 may be disposed perpendicularly skew to and above theengagement axis 530. The angle at which the second conductor bore 540may be formed skew to the engagement axis 530 is preferably greater than45 degrees and less than about 135 degrees, and is preferably about 90degrees. However, as described in connection with later embodiments, thesecond conductor axis 542 may be disposed substantially parallel (aboutzero or about 180 degrees) to the engagement axis 530.

The coupling element 550 is preferably formed as a conductive stud 552formed between a first end 552 a and second end 552 b along a stud axis553 for a stud length 554. The stud length 554 is preferably less than adimension of the connector body 510 that is parallel to the engagementaxis 530. Indeed, when the coupling element 550 is operativelypositioned to couple a plurality of conductors, the coupling element 550is preferably situated completely within all perimeters of the connectorbody 510, so as to inhibit electrical conduction through the couplingelement 550 through accidental outside contact. The stud 552 preferablyhas mating engagement means 556, such as threads 558, formed along atleast a portion of the stud length 554, to cooperate with the engagementmeans 532 provided in the engagement aperture 528, such as at least aportion of the threads 534, provided in the engagement aperture 528. Apreferred material for the stud 552 is stainless steel, copper, or anyother conductive material. The first end 552 is preferably at leastpartially formed as a substantially planar surface disposed preferablyorthogonally to the stud axis 553. The second end 552 b is preferablyprovided with a tool engagement surface 555, which may include a femalehexagonal socket 557, as shown, or other engagement surface.

To use the first embodiment 500 of a connector according to the presentinvention, a plurality of insulated conductors 306″,400 are insertedinto the connector 500, and electrically coupled by the coupling member550. A first insulated conductor 306″ may include an electricallyconductive portion circumferentially surrounded by an electricallyinsulative portion. The conductive portion may be a solid conductor,such as a wire of suitable gauge, a plurality of conductors forming astraight stranded wire, or one or more coiled wires having an at-restturns-per-inch count. Electrically coupled to the conductive portion isan electrically conductive terminal 304″, such as a stainless steelterminal that may be crimped onto the conductor and/or the insulation,as described above. A second insulated conductor 400 may include aelectrically conductive portion circumferentially surrounded by anelectrically insulative portion. The conductive portion may be a solidconductor, such as a wire of suitable gauge, a plurality of conductorsforming a straight stranded wire, or one or more coiled wires having anat-rest turns-per-inch count, and is preferably the latter. At an end ofthe second conductor 400 distal from the connector 500, the conductor400 may terminate in a desired fashion, such as with a custom orconventional electrical plug, socket, jack, etc., or with a functionaltermination such as a stimulating electrode 402, and more preferably astimulating electrode configured to be anchored in animal tissue.

To use the connector 500, the first conductor 306″ is inserted into thesecond conductor bore 540 such that the terminal 304″ is disposed atleast partially within the engagement aperture 528. Preferably, theterminal 304″ abuts a closed end of the second conductor bore 540 toregister the terminal 304″ in a desirable position to help reduceguesswork as to positioning. The first conductor 306″ may be secured tothe connector body 510, such as with adhesive or sealant, or with anonpenetrating set screw. Preferably, along at least a portion of thesecond conductor bore 540, void space that may exist between theinsulated wire 306″ and the bore 540 is at least partially filled withan electrically insulative substance, such as silicone. The process ofdisposing the first conductor 306″ at least partially within theconnector body 510 may be performed generally prior to productpackaging, such as sterile product packaging, or such assembly may beperformed by a user upon opening one or more sterile packages containingthe first conductor 306″ and the connector body 510. Preferably, thoughnot necessarily, after the first conductor 306″ is inserted and/orpositioned, the second conductor 400 is preferably inserted into thefirst conductor channel 538 and at least partially into the engagementaperture 528. If the engagement aperture 528 extends entirely throughthe connector body 510, the second conductor 400 may be pulled throughthe body 510 to a desired length. Once the conductors 306″,400 are at adesired position, the coupling member 550 is placed into electricalcommunication with both conductive portions of the wires 306″,400. Whilethe coupling member 550 may be completely removed from the body 510 toallow insertion of the second conductor 400, the coupling member 550 ispreferably prepositioned at least partially within the engagementaperture 528 prior to the insertion of the second conductor 400. Suchprepositioning may be done generally at the time of manufacture, and themember 550 may be held substantially rotationally stationary in theengagement aperture 528 by, for example, a drop of silicone. One way inwhich such electrical communication may be achieved is by the threads558 cutting through the insulation of the second conductor 400 and thefirst end 552 a abutting the terminal 304″ of the first conductor 306″.The stud 552 may be advanced, such as with a standard L-shaped hex, orother wrench 950 (as shown in FIG. 14), in the engagement aperture 528to a desired position, such as for an instructed number of turns or to adesired torque. Some deformation or deflection of the terminal 304″ mayoccur. Once operatively positioned, the stud 552 preferably is disposedcompletely within all perimeters of the connector body 510.

As mentioned, the conductors 306″,400 may be one or more coiled wireshaving an at-rest (unstretched) turns-per-inch count. The threads 558 onthe coupling member 550 are preferably positioned at a thread pitch thatapproximates (preferably +/−10%) the at-rest turns-per-inch count of a(multi-)coiled conductor, if used.

Connector Mounting Structure

Turning now to FIG. 16, a preferred connector mounting structure 600 isshown. The preferred connector mounting structure 600 includes agenerally planar connector mounting pad 602 adhered to a generallyplanar pad carrier 604. The connector mounting pad 602 is preferably apolyethylene tape material, that may be coated with adhesive on twosides. The pad carrier 604 is preferably formed from a polyesternonwoven tape that is coated with an adhesive on a single side. Themounting pad 602 is preferably adhered to the side of the pad carrier604 that does not include adhesive. The connector mounting structure 600also preferably includes a connector cover strap 608, which ispreferably formed from a polyolefin tape material coated on a singleside with adhesive. The cover strap 608 is preferably adhered to the padcarrier 604, preferably on the side of the pad carrier that does notinclude adhesive. A releasable liner 610 may be provided in aV-formation, with one side of the V adhered to the cover strap 608 andthe other side of the V adhered to the mounting pad 602. Provided on theside of the carrier 604 that is preferably provided with adhesive may bea substantially planar cushion pad 612, which is preferably apolyethylene foam tape material, which may be provided with adhesive ona single side. The substantially planar side of the cushion pad 612provided with adhesive is preferably mated with the side of the carrier604 that is provided with adhesive. Generally, the cushion pad 612 isprovided along a substantially similar or identical length of thecarrier 604 as the connector pad 602 is provided on the opposite side ofthe carrier 604. Also disposed on the adhesive side of the carrier 604is a pair of preferably overlapping release liners 614, which preferablyoverlap across at least a portion of the cushion pad 612. At least oneof the release liners 614 preferably extends longitudinally beyond anedge of the carrier 604 to aid in starting to release the liner from thecarrier 604. To use the connector mounting structure 600, the releaseliner 610 may be removed from the connector pad 602, and an electricalconnector, such as connector 500, may be secured thereto by the adhesiveprovided thereon. The release liner 610 may be further removed from thecover strap 608, and the adhesive side of the strap 608 may overlie andadhere to the connector 500 and the carrier 604. The connector mountingstructure 600 may then further be mounted to a support structure, suchas an external skin surface of a human user patient. The release liners614 may be removed from the adhesive side of the carrier 604, and thecarrier 604 may be adhered to the skin surface, with the cushion pad 612lying in intimate contact with the skin surface. Of course, a connectormounting structure according to the present invention may be constructedwithout the cushion pad 612, and would still fall within thecontemplated scope of the invention.

Percutaneous Lead

Turning now to FIG. 17, a preferred percutaneous lead 400 may bedescribed. The lead 400 preferably includes an electrode 402 thatextends from preferably an insulated conductor 404 having an insulateddiameter 406 of about 10 mils. The insulated conductor 404 is preferably4250 PFA coated 7-strand 316L stainless steel, which is preferably woundabout a mandrel to form an insulated coiled portion 408 of a desiredlength, such as about seven to about nine inches. A portion of a distalend of the conductor 404 is stripped to form the electrode 402. Thestripped portion is preferably coiled on a mandrel to an outsidediameter of about 10 mils to about 15 mils, and then bent at anelectrode angle 410 of about 20 degrees to about 70 degrees. Theelectrode 402 includes an extension 412 and a barb 414. The extension412 has an electrode extension length 416 of about 350 mils to about 450mils, and the barb 414 has a barb length 418 of about half that of theextension length 416, of about 160 mils to about 240 mils. At thejuncture of the electrode 402 and the coiled insulated portion 408, afillet of silicon adhesive 419, such as Nusil Med 1511, is preferablyprovided circumferentially about the lead 400. A test portion 420 of aproximal end of the lead 400 may also be stripped and tinned, and amaximum end-to-end resistance of the lead 400 is preferably about 150ohms. Provided at a tip 422 of the barb 414 of the electrode 402 ispreferably a weld to maintain the conductors of the lead 400 in adesired position. An electrically conductive path in which the lead 400is used preferably has a maximum resistance of about 1300 ohms.

The lead 400 described may be used percutaneously, i.e. introducedthrough the epidermis of an animal. To accomplish such introduction, alead introducer 700 may be used, such as that shown in FIG. 18. Theintroducer 700 extends from a proximal end 702 to a distal end 704, witha lumen 706 extending therethrough. Provided at the proximal end 702 maybe preferably a locking Luer hub 706, which may be electroless nickelplated brass 360 having a Luer taper conforming to ISO 594-1:1986.Extending from the hub 706 towards the distal end 704 is an introducerneedle 708 made from 20 gauge 304 full hard stainless steel thin wallhypodermic tubing with an outside diameter of about 35 to about 36 milsand an inside diameter of about 25 to about 30 mils. The Luer hub 706and needle 708 are preferably coated with 0.1 to 0.2 mils ofelectrically insulative SCS Parylene C conformal coating applied toexternal surfaces. The electrically insulative coating preferablyprovides at least 100 volt minimum dielectric strength. A plurality ofdepth markings 710 are preferably provided along the length of theneedle 708. Preferably, twelve such markings 710 are provided at aspacing of about 400 mils. The markings 710 may be formed, e.g., bylaser etching. At the distal end 704, the needle 708 is preferablyground to a three-face lancet formation, including a point 712, a bevelportion 714, and a non-coring heel portion 716. The cuts to form thebevel 714 and heel portion 716 are all preferably provided at an angleof about 18 degrees from longitudinal parallels to the exterior surfaceof the needle 708.

Percutaneous Lead Placement

FIG. 19 depicts the percutaneous lead 400 having been inserted into theintroducer 700 for use. It may be desirable to provide a protectiveplastic tubular member 720 disposed over the introducer needle 708 forpackaging and safety purposes. Physician experience with placing needlesin muscle using standard locations for clinical electromyography or nearperipheral nerves using standard procedures for nerve block (regionalanesthesia) may be recommended. Lead and/or needle advancement ispreferably to be stopped approximately 0.5-1 cm proximal to the depththat is traditionally used in standard needle insertion techniques.Imaging, such as ultrasound, may be useful during the procedure.

Conventional needle electrodes may be used to deliver test stimulationbefore percutaneously placing a lead, such as the lead 400 previouslydescribed. Local anesthesia may be provided at the discretion of theclinician. Anesthesia may be applied subcutaneously (e.g., lidocaine),topically (e.g., EMLA cream), or both. It is preferable to notadminister the local anesthetic too close to the target electrode sitebecause doing so could affect the response to stimulation. With a userpatient appropriately positioned, a lead entry site should be identifiedon the skin of the patient and cleaned with a standard prep solution tocreate a sterile field. A test stimulation may be delivered through aneedle electrode for identification of a proper target lead placementposition. The stimulator 200 may be mounted to the patch assembly 100.The patch assembly 100 may be adhered to the patient's skin, preferablyoutside of the sterile field. It is preferred to refrain frompositioning the stimulator across the midline of the patient's body fromthe target electrode site to prevent inadvertently passing stimulationcurrent across the heart. A target stimulation site is identified, suchas a target peripheral nerve, and the needle electrode may be placed orattempted to be placed at the target site. The stimulator 200 may beconnected to the needle electrode using a cable, such as the cable 300′previously described, by using the second connector element 303′ or thethird connector element 304′.

The stimulator 200 may be programmed to deliver a test stimulation tothe needle electrode. Programming of the stimulator is further describedbelow. With the stimulus amplitude and frequency set to desired levelsand the pulse duration set to a desired floor value (such as about 20μsec), stimulation may be initiated by pressing and releasing theStart/Stop button 222 d. While stimulation is being delivered, the pulseduration may be slowly increased by slowly (e.g. once every one totwenty seconds, but more preferably once every five to ten seconds)serially pressing and releasing the Increase button 222 c until adesired response to the stimulation is obtained. A desired response mayinclude a desired paresthetic effect and/or comfortable musclecontraction in the target area. If a desired response to the stimulationis not obtained, the needle electrode may be repositioned as necessary,to a location that provides the desired response at a comfortablestimulus intensity. The location of the needle electrode may beidentified and/or logged, or the needle electrode may remain in place,to guide placement of the electrode lead 400. Preferably duringplacement of the electrode lead 400, the cable 300′ is disconnected fromthe needle electrode.

An anticipated pathway for the electrode lead 400 may be visualized bythe clinician, either based on experience or based on the teststimulation previously applied, as described above. If desired, a localanesthetic may be administered subcutaneously, topically, or both at theinsertion site for the electrode lead 400. Again, it is preferable torefrain from administering a local anesthetic too close to the targetelectrode site because doing so could affect the response tostimulation. With the electrode lead 400 situated within its introducer700, as shown in FIG. 19, both may be introduced through the patient'sskin towards the target stimulation site, which may have previously beenidentified by using the needle electrode. Preferably, a test stimulationmay be delivered as the introducer 700 and lead 400 are advanced (atapproximately 1 cm intervals) to optimize the electrode 402 location. Todeliver test stimulation to the electrode 402, the second connectorelement 303′ of the cable 300′ may be clipped to the conductive proximalend of the lead 400 while the first connector element 302′ may beelectrically coupled to the stimulator 200, thus establishing aconductive path from the stimulation generation circuitry in thestimulator 200 to the electrode 402. As with the test stimulationapplied to the needle electrode, the stimulator 200 may be programmed todeliver a test stimulation to the electrode 402. Programming of thestimulator is further described below. With the stimulus amplitude andfrequency set to desired levels and the pulse duration set to a desiredfloor value (such as about 20 μsec), stimulation may be initiated bypressing and releasing the Start/Stop button 222 d. While stimulation isbeing delivered to the electrode 402, the pulse duration may be slowlyincreased by slowly (e.g. once every one to twenty seconds, but morepreferably once every five to ten seconds) serially pressing andreleasing the Increase button 222 c until a desired response to thestimulation is obtained. A desired response may include a desiredparesthetic effect and/or comfortable muscle contraction in the targetarea. If a desired response to the stimulation is not obtained, theelectrode 402 may be repositioned, e.g. advanced, as necessary, to alocation that provides the desired response at a comfortable stimulusintensity. Once a desired response is obtained, the introducer 700 maybe removed from the patient, such as by sliding the introducer needle708 along the lead 400. It may be helpful to apply gentle manualpressure towards the location of the electrode 402 during withdrawal ofthe introducer 700. Another test stimulation may be applied to theelectrode 402 to ensure that the lead 400 has not moved due to theremoval of the introducer 700. At this time, the cable 304′ may bedisconnected from the lead 400 and the stimulator 200 and the patchassembly 100 and stimulator 200 may be removed from the patient's skin.

Lead Placement Near Peripheral Nerves

One goal of peripheral nerve stimulation may be pain relief. Thefollowing paragraphs provide more detailed instructions for placing thelead 400 near two nerves that may be targeted for pain relief: theaxillary nerve (upper extremity example) and the femoral nerve (lowerextremity example). These instructions are presented as possibleapproaches for the clinician's consideration, but are not intended asdefinitive or rigorous descriptions of Lead placement technique. Leadplacement decisions and technique should be determined by the clinician,based on the type and location of the pain being treated, and based onstandard clinical practice. The general guidance provided below can beadapted to other upper and lower extremity peripheral nerves as needed.

As stated, one objective of peripheral nerve stimulation may be toachieve pain relief through paresthesia sensation and/or comfortablemuscle contraction in the target painful area. Test stimulationdelivered via needle electrodes can assist in identifying the optimallead location. Muscle response to electrical stimulation, and thepatient's report of stimulus-evoked sensations (paresthesias) canprovide guidance during test stimulation and lead placement. Also, Leadplacement may be guided by ultrasound or fluoroscopy.

When identifying the percutaneous insertion site for the lead 400, it ispreferable to consider where the patch assembly 100 will be worn inrelation to the lead exit site. It is preferable that the patch assembly100 be placed in a location such that there is minimal to no tension onthe lead. Also, it is recommended that the patch be placed in a locationthat will be comfortable and easily accessible for the patient. Asnecessary, the lead insertion site should be adjusted to meet thesecriteria for optimal location of the patch.

Other considerations when placing the lead 400 and determining thelocation for the lead exit location may be one or more of the following:susceptibility to motion from postural changes, susceptibility topressure from body weight, clothing, or position, and cleanliness andease of access to clean.

As an example, the target nerve may be the peripheral branches of theaxillary nerve located in the deltoid muscle. Needle electrodes may beused to locate the motor point(s) of the deltoid muscle using standardlocations for clinical electromyography. For example, it may bedesirable to contract both the middle and posterior heads of the deltoidmuscle, and thus, two needle electrodes would be used to identify themiddle and posterior deltoid motor points. The motor point of the middledeltoid is identified at the midpoint between the humeral tubercle andthe deltoid tuberosity. With the shoulder fully adducted and in neutralrotation, this location corresponds to approximately 3-4 cm distal tothe most anterior portion of the acromion. The motor point of theposterior deltoid is identified approximately 3-4 cm posterior to themotor point of the middle deltoid. Once these motor points are located(as evidenced by strong but comfortable muscle contractions and/orcomfortable paresthesia sensation evoked during test stimulation), teststimulation may be delivered between the motor points using a thirdneedle electrode to evoke contractions in both heads simultaneously. Ifnecessary, the needle electrode can be repositioned toward the musclewith the weaker response until both heads contract strongly. The lead400 should be placed in a preferred location, as described above. Inthis location, the patch assembly 100 may be placed on the insertion ofthe deltoid muscle at the deltoid tubercle (see FIG. 20) or in analternative location.

FIGS. 21-26 show representative embodiments of the steps thatrepresentative instructions for use can incorporate or direct for thepercutaneous placement of an intramuscular (IM) lead 400 for theactivation of a muscle A and muscle B (e.g., the posterior and middle(lateral) deltoid muscles, respectively) in a system for the relief ofpain, such as shoulder pain. The instructions may include a series ofsteps that can be followed to carry out portion or portions of theprocedure. It is to be appreciated that these series of steps may berevised to place only one, or more than one IM lead(s) to activate onemotor point in one muscle, or to activate two or more motor points intwo or more muscles.

In an exemplary embodiment, the steps may include, but are not limitedto:

1) Clean and prepare the skin surface area above the muscle(s) in whichthe IM lead will be placed. For example, the lateral aspect of theaffected shoulder may first be cleaned with Betadine, and a localsubcutaneous anesthetic (e.g., 2% lidocaine) may be administered.

2) Locate the motor points of two adjacent muscles (A and B) and markthem, e.g., with an indelible marker. For example, the motor points ofthe middle and posterior heads of the deltoid muscle may be locatedusing the standard locations for clinical electromyography.

3) Place a needle electrode (e.g., 24 gauge EMG needle electrode) at theidentified motor point locations for muscle A and B. For example, oneneedle electrode 20 is inserted through the skin towards motor point Aand another needle electrode 22 is inserted through the skin towardsmotor point B (see FIG. 22). It is preferred that the each needleelectrode 20,22 is inserted at least substantially perpendicular to atangent of the skin surface at the respective insertion point.

4) Place a surface stimulation return electrode 24 (e.g. patch 100) inproximity of the area where needle electrode 20 and 22 have been placed,which may also be in proximity of the area in which the percutaneouslead 400 will be placed. Test stimulation may be applied to each needleelectrode 20,22, inserted in muscle A and muscle B respectively, withthe surface electrode 24 providing a return path for the teststimulation. The surface electrode 24 may be placed adjacent to theneedle electrodes 20,22. Its position is not critical to the therapy andit can be moved throughout the therapy to reduce the risk of skinirritation.

5) Electrically couple a pulse generator 26 to a needle electrode 20 or22 and to the return electrode 24 (see FIG. 23). Set the desiredstimulation parameters for test stimulation to be delivered by the pulsegenerator 26. Test stimulation may be delivered using acurrent-regulated pulse generator, for example.

6) Deliver test stimulation to each needle electrode individually (i.e.,one at a time) by slowly increasing the stimulation intensity.Stimulation intensity is defined here as the product of stimulationamplitude and stimulation pulse duration. Increasing the stimulationintensity can be achieved by keeping stimulation amplitude constant andincreasing stimulation pulse duration, by keeping stimulation pulseduration constant and increasing stimulation amplitude, or by increasingboth stimulation amplitude and stimulation pulse duration. For example,the stimulation intensity may initially be set at a very small,sub-sensation and sub-motor threshold level. Then, the stimulationintensity may be increased in small increments (e.g. 10 μs) to determinethresholds, for each motor point, at which the first sensation ofstimulation occurs (T_(SEN)), at which stimulation evokes the firstvisible muscle contraction (motor threshold, T_(MUS)), and at whichstimulation evokes the maximum tolerable muscle contraction (T_(MAX)).

7) Each needle location may need to be adjusted to a location thatprovides the strongest muscle contraction at the lowest stimulationintensity for each muscle. If the thresholds measured are determined tobe high, it may be an indicator that the electrode is placed too faraway from the motor point. Placing the electrode closer to the motorpoint, but not touching the motor point, may reduce one or morethresholds, and the motor point may be found when the thresholdmeasurements are at a desired minimum. For example, if T_(MUS) is closeto T_(MAX), the needle electrode may be repositioned to lower thethreshold such that T_(MUS)<<T_(MAX), thus allowing for a strongcontraction below the maximum tolerable stimulus intensity.

8) Record the stimulation intensity at which the first sensation occurs,at which the first noticeable muscle contraction occurs, and/or maximumtolerable muscle contraction occurs, for both muscle A and muscle B.

9) Determine the location at which both muscle A and muscle B can beactivated simultaneously using one electrode. This determination may bemade by placing a third needle electrode 28 at the approximate midpointbetween the above identified locations of needle electrodes 20,22 forthe motor points of muscle A and muscle B respectively (see FIG. 24).Alternatively

10) Deliver stimulation to the needle electrode 28 in an attempt toactivate both muscle A and muscle B with the one electrode 28. Forexample, deliver stimulation, increasing stimulation intensity untilboth the middle and posterior deltoids muscles (i.e., muscle A andmuscle B) are activated and are producing strong, visible, and palpablemuscle contraction at a tolerable stimulus intensity.

11) If unable to achieve strong contraction of both muscles A and B at atolerable stimulus intensity, remove the electrode 28 and translate itacross the skin surface for a predetermined distance (e.g.,approximately 0.5 cm) closer to the muscle that showed weakercontraction during stimulation applied in step 10, above.

12) Repeat stimulation delivery and placement location correction untilboth muscle A and muscle B contract at the desired level at a tolerablestimulus intensity.

13) Mark, note, and/or record this location with an indelible marker.

14) Record at which stimulation intensity first sensation, firstnoticeable muscle contraction, and maximum tolerable muscle contractionoccurs by stimulation applied through the third needle electrode 28.

At this point in the process, three parameters, T_(sen), T_(mus), andT_(max) have been measured for the three locations, i.e., motor point ofmuscle A, motor point of muscle B, and the location between motor pointof muscle A and B to activate both muscles. The three parameters may behigher for the location in the middle due to its larger relativedistance to the motor points at location A and B compared to bothindividual locations A and B.

For the described one lead approach, the parameters at location A and Bmay be used for guiding the exploration of finding the ideal locationbetween A and B and the expected parameter range for the middlelocation. The parameters at the middle location are then used to programthe parameters for stimulation to be applied through the IM lead to beplaced in the middle depending on the desired application. Anapplication might require sub-sensation stimulation, an applicationmight require sub-motor (but supra-sensation) stimulation, anapplication might require supra-motor threshold stimulation, and yetanother application might require stimulation at the maximum tolerablelevel. For example, the pain relief application described may requirestimulation at T_(max) in the middle location to activate the posteriorand middle deltoid fully at the maximum tolerable stimulation intensity.

15) Remove all three needle electrodes 20, 22, and 28.

16) Identify the anticipated pathway of the percutaneous lead 400. Theentry point of the lead may be a predetermined distance (e.g.,approximately 2 to 3 cm) above the site identified as the location forthe placement between the muscles A and B, such that the lead enters atan acute angle (e.g. less than 45 degrees) relative to a tangent of theskin surface, for example. This placement may aid in lead stability.

17) Administer a local anesthetic (e.g., 2% lidocaine) at the skinsurface and along the anticipated pathway of the lead 400.

18) Insert the percutaneous lead 400 and electrode 402. For example, thelead may be placed percutaneously in the muscle via an introducer needle700 (see FIG. 25), such as an insulated 20 gauge introducer needle.

19) Once the electrode 402 of the lead 400 has reached the desiredlocation (i.e., at or near the final position of needle electrode 28),couple pulse generator 26 to the lead 400 and to the return electrode24, and deliver stimulation to the lead 400 to verify proper placement.Both muscle A and muscle B desirably contract. Desirably, a strong,visible, and palpable contraction is evoked at a stimulus intensity thatis tolerable for the participant.

Although not required, the position of the IM lead 400 or electrode 402may be checked by imaging techniques, such as ultrasound or X-rays(fluoroscopy). Following placement of the lead(s), the portion of theleads which exits the skin may be secured to the skin using coveringbandages and/or adhesives.

20) The stimulation intensity associated with first sensation ofstimulation (i.e., T_(SEN)), first noticeable muscle contraction (i.e.,T_(MUS)), and maximum tolerable contraction (i.e., T_(MAX)), may againbe recorded.

It is preferred that the length of time to identify the optimalplacement and place the IM lead to be less than one hour.

Terminating the Lead

Preferably after the lead 400 is situated at a desired position throughthe skin of a patient, the lead 400 is preferably terminated in aconnector, such as the insulation displacement connector 500 previouslydescribed, which may already have a cable 300″ installed thereon. Theconnector 500 may be provided with an indicator, such as an arrow, toguide lead insertion. The lead 400 may be drawn through the connector500 until a desired length of the lead 400 is remaining between theconnector 500 and the percutaneous exit site. Enough length shouldremain to allow for coiling of the lead for strain relief and so thatthe connector may be placed adjacent to the exit site and preferablyunder the same cover bandage 975. It is preferred to refrain fromplacing the connector 500 or any part of the connector mountingstructure 600 immediately on top of the lead exit site.

Test stimulation may be provided through the cable 300″ and connector500 to ensure that there is an electrical connection between theelectrode 402 and the cable 300″ through the connector 500. Excessproximal length of the lead 400 may be trimmed. Preferably after thelead 400 has been secured in the connector 500, the connector mountingstructure 600 is used, as described above, to secure the connector 500to the skin near the exit site of the lead 400. The connector 500 shouldbe placed on the connector mounting pad 602 such that the lead 400 exitspreferably perpendicular to the longitudinal direction of the padcarrier 604. Excess lead length extending between the connector 500 andthe lead exit site may be coiled to rest against the skin, such as bybeing placed under a waterproof bandage 975, which preferably coversboth the lead exit site and connector 500, and more preferably theentire connector mounting structure 600.

User Interfaces and Usage

As described, the liquid crystal display (LCD) 220 and push buttons 222allow therapy parameters to be set and compliance to be monitored, allowthe user patient to turn stimulation on and off, and allow the userpatient to make changes to the stimulus intensity within a predeterminedstimulation range, preferably controlled and programmed by a clinician.

Button 222 a may be referred to as a Mode button. The Mode button 222 apreferably provides a menu navigation function. Further, the Mode button222 a may be preferably pressed and held for a predetermined time, suchas four seconds, while the stimulator 200 is in one software mode, suchas Clinician Mode, to cause the stimulator 200 to enter a secondsoftware mode, such as User Mode. The Mode button 222 a may also be usedto enter a software mode, such as Clinician Mode.

Button 222 b may be referred to as a Decrease button. The Decreasebutton 222 b may be pressed decrease a treatment parameter currentlydisplayed on the screen 220 or to scroll down through multi-screendisplays, such as logged error codes.

Button 222 c may be referred to as an Increase button. The Increasebutton 222 c may be pressed to increase a treatment parameter currentlydisplayed on the screen 220 or to scroll up through multi-screendisplays, such as logged error codes.

Button 222 d may be referred to as a Start/Stop button. The Start/Stopbutton 222 d may be pressed to turn the stimulator 200 on in apredetermined software mode, such as User Mode. The Start/Stop button222 d may also be used to turn stimulation therapy on and off. Further,the Start/Stop button 222 d may be preferably pressed and held for apredetermined time, such as four seconds, to turn the stimulator 200 offto a standby state.

The slide switch 224 may be referred to as a Lock switch. The Lockswitch 224 may be used to disable the stimulator buttons 222 to preventaccidental button activations. The switch 224 may be moved to a first,locked position to disable the buttons 222, and to a second, unlockedposition, to enable the buttons 222. A lock icon preferably appears onthe screen 220 to indicate when the switch 224 is in the locked positionand the buttons 222 are locked.

Generally, there are preferably two modes of stimulator operation, UserMode and Clinician Mode. User Mode is the operation mode that userpatients preferably use at all times. In User Mode, patients preferablyare able to turn stimulation on and off, view time remaining in atherapy session, and make adjustments to the stimulus pulse durationwithin a predetermined range of parameters, preferably programmed by aclinician. Clinician mode is preferably used by clinicians to programtherapy parameters, view usage information and view any errors that mayhave been logged by the stimulator 200. Clinician Mode is preferably notaccessible by patients. The stimulator 200 may be powered on in eitherUser Mode or in Clinician Mode. To turn the stimulator 200 on in UserMode, the Start/Stop button 222 d may be pressed and released. To turnthe stimulator 200 on in Clinician Mode, it may be desirable to requirea serial combination of buttons 222 to be pressed. For instance, whilethe stimulator 200 is turned off, a clinician may be required to pressand hold the Mode button 222 a while entering a serial combination ofpressing and releasing two or more of the other buttons 222 b,222 c,222d. Such combination, or similar combination, aids to prevent patientsfrom being able to change the detailed stimulation settings.

Once the stimulator 200 is on and in the Clinician Mode, the User Modemay be entered, such as by pressing and holding the Mode button 222 afor a predetermined time, such as four seconds. The display 220preferably displays a message, such as “USER” to indicate that User Modehas been entered. Additionally, it may be desirable to have an automatictransition from Clinician Mode to User Mode after a predetermined timeof inactivity of the buttons 222, such as about five minutes. Suchautomatic transition may be desirable in the event that a clinicianforgets to enter the User Mode, and perhaps sends a user patient on hisor her way after an appointment. It is preferably that the ClinicianMode not be enterable from the User Mode if the stimulator 200 is on andin the User Mode. This is yet another safeguard to prevent user patientaccess to the Clinician Mode and alteration of detailed stimulationparameters.

In Clinician Mode, a clinician may program a range of pulse durationsfrom which a user patient may select during home use. This gives thepatient the flexibility to make minor adjustments to their treatmentwithout the assistance of a clinician. Clinicians are able to program aminimum pulse duration, a “normal” pulse duration (pulse durationdetermined to be optimal), and a maximum pulse duration. The normalpulse duration is preferably equal to or greater than the minimum pulseduration. The maximum pulse duration is preferably equal to or greaterthan the normal pulse duration. If a pulse duration value is set out ofan allowable range, the other two values preferably automaticallyadjust.

In User Mode, a patient may select from a predetermined number ofstimulus intensities (pulse durations), such as the seven intensitiesshown in Table 1. The numbers −3 through +3 represent the relativeintensities of the stimulus in a format that is easy for the patient tounderstand.

TABLE 1 Stimulus Intensities User Selectable Programmed by IntensityClinician −3 Minimum Pulse Duration −2 — −1 — Norm Normal Pulse Duration+1 — +2 — +3 Maximum Pulse DurationThe pulse durations for settings −2, −1, +1, and +2 are preferablycalculated such that the increments between −3, −2, −1, and Norm areequal, and the increments between Norm, +1, +2, and +3 are equal.

Programming the Stimulator

The stimulator may be preferably programmed with default values whichmay then be altered by a clinician. Preferred default values, ranges ofallowable values, and increments of adjustment are given in Table 2. Thedefault values may be restored to the stimulator by depressing a certaincombination of buttons 222, such as by pressing and holding the Decreasebutton 222 b and the Increase button 222 c simultaneously for apredetermined amount of time, such as about four seconds, in theClinician Mode of operation. A confirmatory message is preferablyprovided on the display 220, such as “DEF”, to indicate restoration ofdefault stimulation values. In addition, default factory softwareconditions of the stimulator 200, including erasure of usage and errorlogs, may be restored to the stimulator by depressing a certaincombination of buttons 222, such as by pressing and holding the Modebutton 222 a, the Decrease button 222 b and the Increase button 222 csimultaneously for a predetermined amount of time, such as about tenseconds, in the Clinician Mode of operation. A confirmatory message ispreferably provided on the display 220, such as “FAC”, to indicaterestoration of factory default software conditions.

TABLE 2 Default values, ranges, and adjustment increments for treatmentparameters. Adjusts in increments Parameter Default Minimum Maximum ofAmplitude 20 mA 1 mA 20 mA  1 mA Frequency 12 Hz 5 Hz 25 Hz  1 Hz Pulse20 μsec 20 μsec 200 μsec 10 μsec Duration Minimum Pulse Pulse Pulse 200μsec 10 μsec Duration Duration Duration Maximum Minimum Minimum PulsePulse Pulse Pulse 10 μsec Duration Duration Duration Duration NormalMinimum Minimum Maximum Therapy 6 hours 15 min 12 hours 15 min Time DutyCycle 50% 50% 50% N/A

To program the stimulator 200, it may first be placed in the ClinicianMode of operation. The display 220 may provide a confirmatoryindication, such as “OLIN” to indicate that the stimulator 200 is in thecorrect mode. A stimulus amplitude may then be displayed for adjustment,indicated, for example, by an “mA” on the display 220. The stimulusamplitude may be adjusted to a desired level by using the Decreasebutton 222 b (to decrease the amplitude) or the Increase button 222 c(to increase the amplitude). After the desired stimulus amplitude hasbeen selected, the Mode button 222 a may be pressed. A stimulusfrequency may then be displayed for adjustment, indicated, for example,by an “Hz” on the display 220. The stimulus frequency may be adjusted toa desired level by using the Decrease button 222 b (to decrease thefrequency) or the Increase button 222 c (to increase the frequency).After the desired stimulus frequency has been selected, the Mode button222 a may be pressed.

A stimulus minimum pulse duration may then be displayed for adjustment,indicated, for example, by an “μs” and “MIN” on the display 220. It ispreferable to adjust the stimulation parameters while the stimulation isturned on, to confirm that the resulting stimulus is comfortable andresults in a desired response. Stimulation may be turned on by pressingthe Start/Stop button 222 d. The minimum stimulation pulse duration maybe adjusted to a desired level by using the Decrease button 222 b (todecrease the pulse duration) or the Increase button 222 c (to increasethe pulse duration). If the minimum pulse duration is set to a valuehigher than the normal and/or maximum pulse duration, the value(s) forthe normal and/or maximum pulse duration preferably automaticallyincrease such that they match the minimum pulse duration, thusestablishing a floor pulse duration level. It may be preferable to setthe minimum pulse duration to the pulse duration at which firstobservable response (such as paresthesia or muscle twitch) occurs. Afterthe desired minimum pulse duration has been selected, the Mode button222 a may be pressed.

A stimulus maximum pulse duration may then be displayed for adjustment,indicated, for example, by an “μs” and “MAX” on the display 220. It ispreferable to adjust the stimulation parameters while the stimulation isturned on, to confirm that the resulting stimulus is comfortable andresults in a desired response. Stimulation may be turned on by pressingthe Start/Stop button 222 d. The maximum stimulation pulse duration maybe adjusted to a desired level by using the Decrease button 222 b (todecrease the pulse duration) or the Increase button 222 c (to increasethe pulse duration). If the maximum pulse duration is set to a valuelower than the normal and/or minimum pulse duration, the value(s) forthe normal and/or minimum pulse duration preferably automaticallydecrease such that they match the maximum pulse duration, thusestablishing a ceiling pulse duration level. It may be preferred to setthe maximum pulse duration to the pulse duration at which the maximumtolerable response occurs. After the desired maximum pulse duration hasbeen selected, the Mode button 222 a may be pressed.

A stimulus normal pulse duration may then be displayed for adjustment,indicated, for example, by an “μs” and “NORM” on the display 220. It ispreferable to adjust the stimulation parameters while the stimulation isturned on, to confirm that the resulting stimulus is comfortable andresults in a desired response. Stimulation may be turned on by pressingthe Start/Stop button 222 d. The normal stimulation pulse duration maybe adjusted to a desired level by using the Decrease button 222 b (todecrease the pulse duration) or the Increase button 222 c (to increasethe pulse duration). If the normal pulse duration is set to a valuelower than the minimum pulse duration or higher than the maximum pulseduration, the value for the minimum or maximum pulse duration (the valuethat is out of range) preferably automatically changes such that tmatches the normal pulse duration. It may be preferably to set thenormal pulse duration to the pulse duration at which a strong responseat a comfortable stimulus intensity occurs. After the desired normalpulse duration has been selected, the Mode button 222 a may be pressed.

Upon entering a screen display in which pulse duration (minimum, normal,or maximum) is to be reviewed or adjusted, stimulation preferablyautomatically turns off to avoid sudden changes in pulse duration.Stimulation can be turned on by pressing and releasing the Start/Stopbutton 222 d.

A stimulus therapy time, which is the time for which a stimulus regimemay be delivered and after which stimulation is automaticallydiscontinued, may then be displayed for adjustment, indicated, forexample, by an “HRS” (an abbreviation for hours) on the display 220. Thetherapy time may be adjusted to a desired level by using the Decreasebutton 222 b (to decrease the therapy time) or the Increase button 222 c(to increase the therapy time). After the desired stimulus therapy timehas been selected, the Mode button 222 a may be pressed.

A usage time may then be displayed for review, indicated, for example,by an “HRS” and “USE” on the display 220. Preferably, the amount ofstimulation time since the stimulator 200 was first activated is logged,including any test stimulation that has been delivered. After the usagetime is reviewed, or to proceed to the next menu item, the Mode button222 a may be pressed.

Logged errors may then be displayed for review, indicated, for example,by a first number to the left of a colon and a second number to theright of a colon. The first number preferably indicates or provides anerror code, while the second number preferably provides the number oftimes the error has been logged. The logged errors may be scrolledthrough by, for example, pressing the Decrease button 222 b (to scrollup or down through the logged errors) or the Increase button 222 c toscroll the opposite way. If further parameters are to be reviewed oradjusted, the Mode button 222 a may be repeatedly pressed to cyclethrough the user output screens.

After programming is complete in the Clinician Mode, the stimulator 200may be turned off by pressing and holding the Start/Stop button 222 d,and then turned back on in User Mode by pressing and releasing the samebutton 222 d, or otherwise placed in User Mode. Stimulation may bestarted by pressing and releasing the Start/Stop button 222 d.Stimulation is preferably provided by the clinician to a user patient ateach of the established programmed regimes to confirm that allintensities are comfortable for the patient. If necessary, ClinicianMode may be entered to make modifications to the stimulation parameters,or the regimes may be delivered to the patient while the stimulator 200is in Clinician Mode prior to switching to User Mode.

A battery indicator is also preferably provided on the display 220. Whenthe battery indicator provides indication of low battery, such as by ablinking indication, the power source for the stimulator 200 should bereplaced, such as by replacing a patch assembly 100 if the power sourceis provided thereon, such as by the patch battery assembly 110.

System Use

When it is desirable for a user patient to receive electricalstimulation, the stimulator 200 may be mounted to a patch assembly 100,and the patch assembly 100 may be mounted to the patient's skin.Optionally, for some patients, it may be desirable to apply a skinbarrier product to the area where the patch assembly 100 will beadhered, to form a protective barrier on the skin. It is preferable toorient the stimulator 200 and patch assembly 100 such that there isminimal or no tension on the cable 300″ and the lead 400 and it is easyfor the person who will be operating the stimulator 200 to read thedisplay 220. The first cable 300 may be used to couple the stimulator200 to the electrode 402, to complete an electrical path through thelead 400, the connector 500, and the third cable 300″. For instance thefirst connector element 302 may be mechanically and electrically coupledto the stimulator 200 and the second connector element 304 may bemechanically and electrically coupled to the first connector element302″ on the third cable 300″. Optionally, the cables and/or connectorsmay be secured to the patient's skin using one or more waterproofbandages 975, as shown in FIGS. 20 and 21. Preferred bandages 975 to beapplied to the lead exit site are preferably waterproof and primarilyclear and may have a non-stick area in the middle such that the adhesiveportion of the bandage 975 does not come in contact with the lead 400(e.g., 3M Nexcare™ Waterproof Bandages, Knee and Elbow 582-10, 2⅜″×3½″,or equivalent). If the adhesive portion of the bandage 975 comes incontact with the 400, there may be an increased risk of putting tensionon the lead 400 when the bandage 975 is later removed. Applying tensionon the lead 400 is undesirable as such forces can cause the electrode402 to move from its intended location.

Stimulation may then be provided to and adjusted by the user patient.The adjustment can be accomplished by unlocking the switch 224 (if itwas previously locked) and then using the Decrease button 222 b or theIncrease button 222 c to adjust stimulation.

When stimulation is complete or it is otherwise desirable to removecomponents according to the present invention from a user patient, thestimulator 200 may be turned off, and the patch assembly 100 and cablesmay be disconnected and removed. The lead 400 may be trimmed to removethe connector 500, or the connector 500 may remain coupled to the lead400 to aid in extraction. While applying steady tension to the exposedportion of the lead 400, the lead 400 may be gently pulled out of thepatient's body. The lead 400 uncoils and the barb 414 straightens as thelead 400 is being pulled. It is preferred to inspect the lead 400 forsigns of damage. If the lead 400 appears to be broken, the patient maybe instructed to report any signs of pain, redness, swelling, discharge,or the appearance of a skin abscess. The lead exit site should becleaned and bandaged as usual. It is possible that a fragment (orfragments) of the electrode 402 will break off and remain in the bodyafter lead removal. If the lead 400 is being removed due to aninfection, all fragments should be removed as well. In all other cases,clinical judgment may be used to determine whether or not the fragmentsshould be removed. If fragments remain, the patient may be instructed toinspect the site and report signs of infection or granuloma. Shouldsigns of infection appear, the fragments should be removed via anoutpatient procedure. Any abscess may be lanced and the fragment(s)should be removed. A topical antibiotic may then be applied.

Placebo Mode of Operation

Additionally or alternatively, a sham or placebo mode of operation maybe provided in the stimulator 200, preferably through software functionswitching. A sham mode of operation may be useful in conducting aplacebo study or a double blind stimulation study. In sham mode,virtually all aspects of the stimulator operation are preferablysubstantially similar or identical to that of normal (non-sham) mode,especially in presentation to a user patient and/or clinician. Forexample:

The user may be presented with an indication by the stimulator 200, suchas an identifier on the display 220, that stimulus is being delivered.

There are preferably no hardware, device, cable/lead, or labelingdifferences on the stimulator 200.

Device implantation, setup and control are preferably identical tooperation in non-sham mode.

The treatment (albeit sham) time is, or time of purported stimulation,is preferably logged and may be displayed as if actual stimulation werebeing delivered.

The battery indicator is preferably modified to appear as if the batterywere draining similarly to normal use.

Sham mode may be entered through a software configuration, which may notbe obvious to the user patient and/or clinician. For instance, sham modemay be entered by pressing a plurality of buttons 222 simultaneously fora predetermined amount of time, or by serially pressing and releasing asequence of buttons 222, and may require that the stimulator 200 appearto be turned-off while such sequence is entered. The stimulator 200 mayprovide an indication of sham mode, such as by displaying an indicationof a software mode that ends in the numeral 5, whereas a softwareversion for normal mode of operation may end in a numeral 0.

Case Example

The subject was a 57-year old man musician with medical history ofhypertension, hyperlipidemia, and glaucoma who developed neck and leftshoulder pain with radiation to his left arm as a result of a motorvehicle collision 20 months prior to enrollment. He underwent x-rayimaging studies of his cervical spine and left shoulder, both of whichwere without acute or degenerative abnormality. No evidence ofradiculopathy or plexopathy was found on electromyographic study of hisleft arm. He experienced persistent left shoulder pain with resolutionof other symptoms and underwent an ultrasound guided subacromialinjection of kenalog and lidocaine 16.5 months before enrollment. Duringthe injection, it was noted that he had mild tendinopathy of themidsubstance of the supraspinatus muscle by ultrasound examination. Heexperienced mild relief as a result of the injection but his leftshoulder pain persisted and he was referred for physical therapy. Hecompleted six visits of physical therapy and was discharged 12 monthsbefore enrollment in the study in connection with the present inventionwith a home exercise program having only intermittent and limited pain.Five months before enrollment in this study, his pain worsened withoutprovocation in spite of continued home exercise program. Just prior toenrollment he was taking acetaminophen and acetylsalicylic acid forpain.

On pre-procedure examination the subject exhibited no shouldertenderness. He had 5 out of 5 muscle strength (Medical Research CouncilScale) in internal rotation, external rotation, and abduction. Heexperienced a 8 out of 10 pain (0 being no pain, 10 pain worstimaginable) with Neer's sign that reduced to 0 of 10 with subacromialinjection of 5 cc of 2% lidocaine. He did not have any evidence ofoverlying skin infection of the affected shoulder. He was not usingopiate medications for pain relief. He was not receiving outpatienttherapies for shoulder pain. He did not have any confounding conditionssuch as ipsilateral upper limb lower motor neuron lesion, Parkinson'sdisease, spinal cord injury, traumatic brain injury, multiple sclerosis,or complex regional pain syndrome. Baseline pain, pain interference,shoulder disability, and range of motion (ROM) are shown in Table 3.

TABLE 3 Baseline, during treatment, and post-treatment outcome measures.Start 1 4 12 of week week week week weeks weeks Baseline Stim 1 2 3 postpost post BPI-3 8 7 6 3 2 1 0 0 BPI-9 5.7 5.4 4 0.7 0 0.7 0 o DASH 34.20.8 1.7 0 0.8 Shoulder Flexion 129 155 170 165 180 (degrees) ShoulderAbduction 108 173 170 180 180 (degrees) Shoulder Ext Rotation 76 75 8083 79 (degrees) PPT Affected Deltoid 5.6 9.0 8.1 9.3 5.9 5.9 (kg/cm²)PPT Contralateral 5.7 7.4 9.3 6.2 6.4 6.9 Deltoid (kg/cm²) PPTContralateral Tibialis 6.4 6.1 8.2 8.8 4.5 8.4 Anterior (kg/cm²) BPI-3:Worst pain in the last week, 0 (None)-10 (Worst imaginable) BPI-9:Average of the scores for the seven domains on a 0 (no interference)-10(complete interference) with general activity, mood, walking ability,normal work, relations with other people, sleep, and enjoyment of lifeduring the last week DASH: a measure of physical function and symptomsin people with musculoskeletal disorders of the upper limb ranging from0 (no disability) to 100 (complete disability Shoulder Flexion: Measuredby handheld goniometer with patient standing Shoulder Abduction:Measured by handheld goniometer with patient standing Shoulder ExternalRotation: Measured by handheld goniometer with lying supine, startingposition of hand on abdomen PPT: Pressure-Pain Thresholds-The amount ofpressure (kg/cm²) from a handheld algometer where a sensation ofpressure first changes to pain.The average of 3 measurements at eachlocation is reported.

The formal 4-month intervention protocol included electrodeimplantation, 1-wk of electrode stabilization, 3-wks of PNS treatment,and 3-months of follow-up. The primary outcome was the Brief PainInventory Short-form Question 3 (BPI 3), which rates the “worst pain” inthe prior week on a 0-10 numeric rating scale, where 0 indicates “nopain” and 10 indicates “pain as bad as you can imagine.” Secondaryoutcomes were: 1) Brief Pain Inventory Short-form Question 9 (BPI 9), ameasure of pain interference with daily activities, including generalactivity, mood, walking ability, normal work, relations with otherpeople, sleep, and enjoyment of life during the last week on a 0-10numeric rating scale, where 0 indicates “does not interfere” and 10indicates “completely interferes.” The BPI 9 score is the average of thescores for the seven domains; 2) the Disabilities of Shoulder, Arm, andHand (DASH) questionnaire, a measure of physical function and symptomsin people with musculoskeletal disorders of the upper limb ranging from0 (no disability) to 100 (complete disability); 3 the Patient GlobalImpression of Change (PGIC), a 6-point subjective measure of change inactivity limitations, symptoms, emotions, and quality of life due tosymptoms since the beginning of treatment; 4) pain-free range of motionof the glenohumeral joint (internal rotation, external rotation, andabduction); and, 5) Pressure-pain threshold measurement (PPT) of thedeltoid of the affected shoulder, contralateral shoulder, andcontralateral tibialis anterior. The PPT is a measure of deep somatictissue sensitivity, indicated by the amount of pressure (kg/cm2) from ahandheld algometer where a sensation of pressure first changes to pain.The average of 3 measurements at each location is reported.

The skin overlying the deltoid muscle was cleaned with povidone-iodinetopical antiseptic. Monopolar needle electrodes were insertedperpendicular to the skin surface at the motor points of middle andposterior deltoids. Motor points were confirmed by stimulating eachmuscle separately and demonstrating strong contraction of the middle andposterior deltoids. A third needle electrode was placed at a midpointbetween the two motor points. The position and depth of the electrodeand the pulse duration were iteratively adjusted until strongcontraction of both heads was achieved.

A 20-gauge insulated introducer loaded with a percutaneous lead was theninserted perpendicular to a tangent of the skin surface to the depth andlocation indicated by the third needle electrode. The characteristics ofthe percutaneous lead have been previously described. The electrode wassupplied with stimulation to verify proper position. Pressure wasmaintained at the skin surface to anchor the electrode's barb in thebelly of the muscle and the introducer was withdrawn leaving theelectrode in place. Stimulation was delivered to the electrode again toensure proper placement. A dry sterile dressing was placed over theelectrode and an occlusive dressing was applied. Prior to leaving theclinic, the subject was instructed on the proper care of the lead exitsite. He returned 48-hours later for examination of the skin.

Following a one week stabilization period, the stimulator was connectedto the lead and parameters were set to stimulate the middle andposterior deltoids at 12 Hz and 20 mA with a pulse duration of 60 μs.The stimulation provided strong contraction of both deltoids. Thesubject was prescribed 6-hrs of stimulation per day. The stimulatorcompleted a cycle every 30 seconds consisting of 5 seconds ramp up, 10seconds maximum stimulation, 5 seconds ramp down, and 10 secondsrelaxation. During the 3-wk stimulation phase he was contacted bytelephone weekly and queried for pain intensity, adverse events, andmedication usage.

At the end of the 3-wk stimulation phase the subject returned forevaluation of primary and secondary endpoints including BPI 3, BPI 9,the DASH, PGIC, pain free ROM, and PPT measurement. Medication usage andadverse events were also recorded. Compliance data were captured by thestimulator datalogger. The electrode was then removed by gently pullingon the exposed end of the lead. He underwent anterior-posterior andscapular-Y view radiographs of the shoulder for surveillance forretained electrode fragments. He returned at 1, 4, and 12-wkspost-treatment for skin evaluation and outcomes assessments.

The subject tolerated the implantation and stimulation test procedurewell. The 3-wk stimulation protocol was completed with adverse events ofmild discomfort when flexing his shoulder simultaneously with receivingstimulation and a localized tissue inflammation granuloma at the site ofthe electrode that resolved by his 1-month follow-up. The subjectreported 100% compliance with the protocol, although the stimulatorrecorded 94% compliance. The outcome measurements for different studytime points are listed in Table 3. The subject experienced 75.0% and100% reduction in pain (BPI 3) at end of treatment relative to baselineand at 3 months post-treatment, respectively. He used aspirin oracetaminophen rarely in the follow-up period, and denied use at his3-month follow-up. There was improvement in pain related quality of life(BPI 9) to where he had no pain interference at the 1 and 3 monthfollow-up visits. His arm function improved with a 97.6% reduction inhis DASH score. This was confirmed by the Patient Global Impression ofChange Scale, which was rated “very much improved” from end of treatmentthrough the 3-month follow-up. Pain-pressure thresholds measured at theaffected deltoid, non-affected deltoid, and tibialis anterior wereincreased at all points after baseline.

This working example describes the first subject treated with asingle-lead PNS system for SIS. After three weeks of electricalstimulation, he experienced substantial pain reduction that wasmaintained for at least three months after completion of treatment. TheBPI 9, DASH, PGIC, pain free ROM, and PPT data suggest that theintervention might also reduce impairment, and improve function, andimprove quality of life.

The mechanism of pain relief may have been the result of improvement inbiomechanics of the subject's shoulder, as evidenced by improved ROM,though PNS resulting in pain relief in stroke survivors with chronicshoulder pain has been achieved with inconsistent improvements inbiomechanics. Alternatively or additionally, stimulation oflow-threshold myelinated primary afferents may decrease the response ofthe dorsal horn neurons to unmyelinated nociceptors. This is similar tothe purported mechanism in which transcutaneous electrical nervestimulation (TENS) reduces pain. However, the duration of pain reliefthis subject has experienced would not be expected with, nor has it beenthought to be achievable by, treatment by TENS.

Additionally or alternatively, PNS delivered according to the presentinvention may reduce chronic pain by altering maladaptiveneuroplasticity in the central nervous system that causes centralhypersensitivity. There is evidence that chronic pain can be perpetuatedby maladaptive neuroplastic changes within the central nervous system.Evidence of central hypersensitivity has been demonstrated by lowerlocal and distal PPTs in those with chronic SIS compared to controls.This subject had improvements in local and distal PPTs, demonstratingthat a central mechanism may be modulated through PNS. That is, in thechronic phase of SIS central sensitization, a form of maladaptiveneuroplasticity, may have a dominant role in pain perception. Whileacute injury is often initiated and maintained by inflammatoryprocesses, chronic injury likely reflects perturbations within theneural axis involving both spinal and supraspinal neural structures.This is likely the reason that treatments appropriate for the acutestage of SIS are no longer appropriate for those who experience chronicpain from SIS. Thus, reversal or bypass of maladaptive neuralplasticity, because same is a pain mediator, is a target of this noveltreatment.

Treatment of chronic pain with PNS may be understood with reference toupdated conceptual framework of pain by Melzack, the neuromatrix theoryof pain and the theory of central sensitization. The neuromatrix theoryposits that pain is a multidimensional experience produced byneurosignature patterns within the neuronal network of the brain. Thesepatterns can be produced by sensory inputs (as in nociceptive pain) orlack of sensory inputs (as in phantom limb pain). The actual experienceof pain is produced by the output of a neuronal network rather thansensory input; however, sensory input can be altered by centralsensitization. Central sensitization is an increase in the function ofneurons and circuits in nociceptive pathways that can become a triggerfor the painful neurosignature pattern. The pathways susceptible tocentral sensitization are widespread within the CNS and includelocations from the dorsal horn to the prefrontal cortex. Failure ofhomeostatic mechanisms allow persistence of central sensitization or thepain provoking neurosignature pattern after the injury resolves, whichcreates a chronic hypersusceptibility to pain from normally innocuousmovements.

Neuroplastic changes of the central nervous system associated withchronic pain have been shown to lead to hypersensitivity. Thehypersensitivity is displayed as local and generalized lowered painthresholds, exaggerated pain response to painful stimulation,enlargement of painful areas, and lower threshold for spinal reflexes.Evidence of this hypersensitivity in chronic SIS has been shown withreduction in pressure pain thresholds in local (primary hyperalgesia)and distant pain-free areas (secondary hyperalgesia) compared tocontrols without shoulder pain. The pressure-pain thresholds werecorrelated with pain severity symptoms (lower shoulder pain wasassociated with higher pain thresholds). Evidence of reduced painthresholds associated with central nervous system changes has been foundin subjects with chronic pain who displayed a lower spinal reflexthreshold and lower pressure pain thresholds when compared to controlswithout chronic pain.

There is also evidence that the hypersensitivity is preceded by chronicpain. A longitudinal population study has shown that those who acquiredchronic pain developed mechanical hypersensitivity, as measured bypressure pain thresholds, whereas stable thresholds were observed inthose who did not develop chronic pain.

To alter this maladaptive neuroplastic change, and thus alter a painexperience, preferably by reducing pain, a shift in neural networksneeds to occur (whether excitatory or inhibitory) causing a shift to aneurosignature pattern that does not confer the experience of pain.Therapeutic electrical stimulation delivered according to embodiments ofthe present invention activates dormant neuronal networks that, whenactivated, disrupt the pathophysiological neuronal networks and therebydiminish symptoms. Not only can electrical stimulation be used tocontrol acutely activated networks, but previously dormant networks canbecome persistently activated by a repetitive electrical stimulationprotocols. IM PNS mediated muscle contraction provides physiologicactivation of muscle spindles and golgi tendon organs, which in turnprovide patterned afferent input to the CNS This differentiates IM PNSfrom spinal cord stimulation, peripheral nerve field stimulation andTENS.

Thus, electrical stimulation mediated sensory modulation can be used tosustain functional reorganization of maladaptive neuroplastic changes ofthe nervous system that is associated with chronic pain.

The foregoing is considered as illustrative only of the principles ofthe invention. Furthermore, since numerous modifications and changeswill readily occur to those skilled in the art, it is not desired tolimit the invention to the exact construction and operation shown anddescribed. While the preferred embodiment has been described, thedetails may be changed without departing from the invention, which isdefined by the claims.

We claim:
 1. A method comprising the steps of: placing an electrode insubepidermal tissue of a human; and delivering electrical stimulationthrough the electrode, wherein, after the delivering step, a level ofpain perceived by the human, wherein the pain was caused by or occurringsecondarily to subacromial impingement syndrome, is reduced.
 2. A methodaccording to claim 1, wherein during the delivering step, a level ofpain perceived by the human, wherein the pain was caused by or occurringsecondarily to subacromial impingement syndrome, is reduced.